The present invention is broadly applicable for stripping unwanted metallic deposits from chemically resistant substrates and more particularly, for chemically removing unwanted metal plating deposits from the contact tips of electroplating work racks and the like.
It is conventional practice in the field of electroplating, to support work pieces to be plated on a work rack comprised of a chemically resistant metal such as titanium or stainless steel or a steel work rack provided with a protective coating such as a plastisol coating thereover. Electrification of the work pieces while suspended in a electrolyte is achieved by stainless steel or platinumized titanium contact tips on the rack disposed in electrical contact with the work pieces. During the electroplating operation, an unwanted deposit of the metal being plated builds up on the contact tips interfering with the efficiency and consistency of the electroplating operation. Accordingly, it is common practice to subject such plating racks to mechanical or chemical cleaning treatments to remove the unwanted accumulation of deposits from the contact tips.
A variety of mechanical and chemical techniques have heretofore been used or proposed for removing unwanted deposits from contact tips of electroplating racks to maintain optimum operating efficiency. Typical of such prior art techniques are those disclosed in U.S. Pat. Nos. 3,015,630; 3,104,167; 3,367,874; 3,399,143 and 3,856,694. While such prior art techniques and compositions as disclosed in the aforementioned patents have been satisfactory in removing certain metallic deposits, a continuing problem associated with such prior art techniques has been the relatively low rate at which the metallic deposits are stripped, the comparatively low capacity of the stripping composition for the metals stripped necessitating frequent replenishment, the selectivity of the specific metals which can be satisfactorily stripped and the inability to strip other metals necessitating alternative stripping compositions and the waste treatment facilities required for treating such stripping compositions in order that they can harmlessly be discharged to waste.
The present invention overcomes many of the problems and disadvantages associated with prior art techniques and compositions by providing a stripping composition and method employing the composition which has increased capacity for the dissolved metal ions, which initiates the stripping action more quickly and further provides for an increase in the rate at which the deposits are stripped, which is applicable for stripping a broader range of metallic deposits including metal alloys such as nickel-iron alloys as well as composite multi-layered deposits, and which required comparatively simple waste treatment facilities for treatment prior to discharge to waste.